The present invention relates to imaging systems and, more particularly, to apparatus for developing an image on plain paper wherein a color precursor is associated with an imaging sheet in an image-wise pattern and a film of developer material is subsequently associated with the imaging sheet to produce an image.
Photosensitive imaging systems employing microencapsulated, radiation-sensitive compositions, also known as cylithographic imaging systems, are the subject of U.S. Pat. Nos. 4,399,209; 4,772,541 and 4,842,976; commonly assigned to The Mead Corporation. These imaging systems are characterized in that an imaging sheet, including a layer of microcapsules containing a photosensitive composition in the internal phase, is image-wise exposed to actinic radiation. In the most typical embodiments, the photosensitive composition is a photopolymerizable composition including a polyethylenically unsaturated compound and a photoinitiator and is encapsulated with a color precursor. Exposure image-wise hardens the internal phase of the microcapsules. Following exposure, the imaging sheet is subjected to a uniform rupturing force by placing the sheet in contact with a layer of developer material on an intermediate developer sheet and passing the sheets through the nip of a pair of pressure rollers, whereupon the color precursor is transferred to the developer sheet where it reacts to form an image.
U.K. Patent Application GB A 2202641 discloses an apparatus for copying on plain paper or cloth using the cylithographic system wherein a wax is incorporated in the developer layer. In one embodiment, the apparatus performs two transfer steps. First, the developer layer of an intermediate developer sheet is transferred to plain paper by passing the developer sheet and paper between pressure rollers. Second, the image-wise exposed imaging sheet is juxtaposed to the plain paper to form an image on the paper. In another embodiment, both the microcapsules and developer are layered on a recording medium which is image-wise exposed. The layers are passed through pressure rollers and the developed image is transferred to plain paper by passing the recording medium and paper through a second set of pinch rollers.